IEEE 802.11 is a set of media access control (MAC) layer and physical layer (PHY) specification for implementing wireless local area network (WLAN) communication, called Wi-Fi, in the unlicensed (2.4, 3.6, 5, and 60 GHz) frequency bands. The standards and amendments provide the basis for wireless network products using the IEEE 802.11 frequency bands. IEEE 802.11 plays an important role in the growing application of Indoor and Outdoor Location. The key applicable Wi-Fi technology is that of ranging using time-of-flight (TOF) ranging measurements defined in IEEE 802.11v. Once the distance between devices is measured, the information can be used to determine device location.
Point-to-point measurement enhancements using iterative measurements, such as Fine Timing Measurement (FTM), have been proposed in IEEE 802.11-REVmc for Indoor Location. Based on FTM, an initiating station exchanges FTM frames with a responding station to measure the time-of-flight (TOF) or the Round Trip Delay (RTD/2). The initiating station then computes its range to the responding station. To calculate a station position, the station performs ranging measurements with multiple access points (APs) via FTM frame exchange and obtains AP's positions. Typically, FTM positioning requires the initiating station to exchange FTM frames with multiple responding APs for TOF measurements in order to determine its absolute location. For 3D positioning, the station needs to exchange FTM frames with four APs in order to determine its absolute location.
The FTM protocol suffers from a list of drawbacks. First, the station possibly needs to switch to different channels in which the APs operate on. Second, the station needs to consume high power due to long session of FTM frame exchange. Third, dense AP deployment is required. Fourth, FTM traffic load increases when more stations perform positioning. The FTM protocol overhead can be substantial if all stations in a dense environment need to perform ranging independently.
Many wireless devices often operation in one or more groups, such as a P2P group. For some applications involving a group of wireless devices, not every station needs to determine its location using FTM. For example, coarse location information is shared among group members. The location determination activities of group members can be managed by a Location Group Leader (LGL), e.g., the GO (Group Owner) of a P2P network. Accordingly, it is desired to have a method for doing Group Location in order to lower protocol overhead and provide more meaningful group related location information.